Technical Field
The present invention relates to semiconductor processing, and more particularly to electrical fuses (eFuses or efuses) integrated into middle of the line (MOL) structures.
Description of the Related Art
Electrical fuses (efuses) are employed in the semiconductor industry to implement array redundancy, field programmable arrays, analog component trimming circuits, chip identification circuits, etc. An electrical fuse typically includes an anode, a cathode, and a fuselink. The fuselink is a narrow strip of a conductive material such as a metal adjoining the anode and cathode, which may also be composed of a metal. During programming of the electrical fuse, a positive voltage bias is applied to the anode and a negative voltage bias is applied to the cathode.
As electrical current flows through the fuselink having a narrow cross-sectional area, the temperature of the fuselink is elevated. A high current density combined with the elevated temperature at the fuselink facilitates electromigration of the conductive material. The conductive material is electromigrated under these conditions from the portion of the electrical fuse structure, thereby increasing the resistance of the electrical fuse structure.
Increased local current density has been obtained by the modification of the layout of the fuse. For example, a two-dimensional “dog-bone” shape fuse element having a small cross-sectional area between large cathode and anode pads increases local current density, and has been adopted in the semiconductor industry as eFuse elements for better process control and higher programming efficiency. eFuses have been planar in their overall design, which takes up valuable real-estate on a chip.